Fire alarm systems are often installed within commercial, residential, educational, or governmental buildings, to list a few examples. These fire alarm systems typically include control panels and fire detection devices, which monitor the buildings for indicators of fire (e.g., smoke, fire, rises in temperature). Often, the fire detection devices include individually addressable smoke detectors that are part of a networked fire alarm system. The smoke detectors send event data to the control panel, which analyzes the received event data and generates an alarm if smoke is detected by one or more of the smoke detectors.
In another configuration, the fire alarm system is comprised of standalone or independent smoke detectors. This type of system is often implemented in residential buildings where there is a smaller area to monitor and building code requirements are more lenient. While each detector operates independently from the other detectors of the system, the detectors are often interconnected such that if one detector is activated into an alarm state, then all of the detectors enter the alarm state.
Two common types of fire detection devices are photoelectric (or optical) smoke detectors and ionization smoke detectors. The optical smoke detectors generally include a baffle system, which defines a detection chamber. The baffle system blocks ambient light from an ambient environment while also allowing air or smoke to flow into the detection chamber. A smoke detection system within the detection chamber detects the presence of smoke. Typically, the smoke detection system includes a chamber light source and a scattered light photodetector. When smoke fills the detection chamber it causes the light from the chamber light source to be scattered within the chamber and detected by the scattered light photodetector. Once a predefined amount of light is received by the scattered light photodetector, an alarm condition is generated. The ionization smoke detectors also typically have a detection chamber containing an ionizing radioisotope to ionize the air in the detection chamber. When smoke fills the detection chamber, the electronics of the smoke detector detect a change caused by the ionization of the smoke. In response to the change in current, an alarm condition is generated. While ionization smoke detectors also include a baffle system to protect the detection chamber, the baffle system is typically designed to prevent moisture from entering the detection chamber because it can affect the accuracy of the smoke detector.
Currently, building codes often require that the fire detection devices be tested annually. This annual testing is performed because smoke detectors, for example, have a number of different failure points. For example, the electronics and/or optics of the detector can fail. Alternatively, the baffle systems can become dirty and clogged over time. Additionally, it is not uncommon for the smoke detectors to be painted over or for insects or spiders to build nests or webs in the detectors.
The annual testing for smoke detectors is commonly completed by a technician performing a walkthrough test. The technician walks through the building and manually tests each of the detectors of the fire alarm system. Typically, the technician uses a special testing device. In one example, the testing device includes a smoke generator housed within a hood at the end of a pole. The technician places the hood around the fire detection device and the smoke generator releases artificial smoke near the detector. If the smoke detector is functioning properly, it will trigger in response to the artificial smoke. The technician repeats this process for every smoke detector of the fire alarm system.
Self-testing fire detection devices have been proposed. In one specific example, a self-test circuit for a smoke detector periodically tests whether the sensitivity of a scattered light photodetector is within a predetermined range of acceptable sensitivities. If the sensitivity of the scattered light photodetector is out of the predetermined range, then a fault indication is produced.